Fuselage door for pressurized aircraft

Abstract

A fuselage door for a pressurized aircraft fuselage in which the hoop tension loads caused by cabin pressure are carried through the door rather than around the door. Stationary interlocking moldings in the door and fuselage door seat transfer loads through the door-fuselage intersection. The interlocking portions of the moldings have a sloped engaging portion having an angle such that the inward directed force component of tension due to a pressure differential is less than the outward directed force from cabin pressure on the door.

I claim: 
     
       1. A door assembly for a pressurized vessel, the pressurized vessel having a curved vessel wall with an outer surface and a door opening, the door assembly having a door for closing and sealing the door opening in the vessel wall, the door assembly comprising; a door engaging seat facing inward on a perimeter portion of the door opening;   a vessel engaging seat facing outward on a perimeter portion of the door which mates with the door engaging seat, the vessel engaging seat abutting and being pressed against the door engaging seat by an outward directed force component resulting from internal pressure in the vessel;   the door engaging seat having a door engaging face which faces inward and away from the opening and is oriented at a selected acute angle relative to a line perpendicular to a portion of the outer surface of the vessel wall nearest the door engaging seat; and   the vessel engaging seat having a vessel engaging face parallel to and mating with the door engaging face when the door is closed, wherein the internal pressure in the vessel creates tension which is transferred by the mating faces through the door.   
     
     
       2. The door assembly of claim 1 wherein the mating faces result in an inward directed force component on the door due to the tension, the inward directed force component being less than the outward directed force component on the door. 
     
     
       3. The door assembly of claim 1, wherein the vessel wall has an inner surface spaced inward from the outer surface and wherein the inward facing surface of the door engaging seat is beveled, providing the door opening at the outer surface of the wall with smaller dimensions than at the inner surface of the vessel wall. 
     
     
       4. The door assembly of claim 1, wherein: the door engaging seat comprises two inclined portions which are located in separate planes and inclined relative to the outer surface of the vessel wall; and   the door engaging face is a step located between and joining the inclined portions to each other.   
     
     
       5. The door assembly of claim 1, further comprising a seal located on one of the seats for sealing against the other of the seats. 
     
     
       6. A door assembly for a generally cylindrical pressurized vessel, the pressurized vessel having a curved vessel wall with an inner surface and an outer surface and a door opening, the door opening having two side edges which are transverse to the axis and curved along a circumferential portion of the vessel, the door assembly having a door for closing and sealing the door opening in the vessel wall, the door assembly comprising; a door engaging seat extending around a perimeter of the door opening, the door engaging seat having an inward facing surface which is inclined relative to the inner and outer surfaces of the vessel wall;   a vessel engaging seat on a perimeter of the door, having an outward facing surface which mates with the inward facing surface of the door engaging seat to retain the door closed;   a door engaging face on the door engaging seat which faces generally away from the opening, the door engaging face being oriented at a selected acute angle relative to a line perpendicular to a portion of the outer surface of the vessel nearest the door engaging seat; and   a vessel engaging face on the vessel engaging seat which is parallel to and engages the door engaging face when the door is closed, wherein internal pressure in the vessel creates tension which is transferred through the door by the mating faces.   
     
     
       7. The door assembly of claim 6, further comprising: a latch for securing the door within the door opening.   
     
     
       8. The door assembly of claim 6 wherein the selection of the acute angle for the mating faces results in an inward directed force component on the door due to the tension, the inward directed force component being less than the outward directed force component on the door. 
     
     
       9. The door assembly of claim 6, wherein: the inward facing surface of the door engaging seat comprises inner and outer inclined portions which are located in separate planes; and   the door engaging face is a step located between and joining the inner and outer inclined portions.   
     
     
       10. The door assembly of claim 6, further comprising a seal located on one of the seats for sealing against the other of the seats. 
     
     
       11. The door assembly of claim 6, wherein the perimeter of the door opening has upper and lower edge portions which are generally straight and parallel with the axis of the vessel; and wherein the door engaging face at the upper and lower edge portions is generally hook-shaped.   
     
     
       12. A door assembly for a generally cylindrical pressurized aircraft fuselage, the fuselage having a curved wall with an inner and outer surface and a generally rectangular door opening, the door opening having a perimeter with top and bottom straight portions generally parallel with an axis of the vessel and two curved side portions extending circumferentially, the door assembly having a door for closing and sealing the door opening, the door assembly comprising; a door engaging seat on the fuselage at the curved side portions, the door engaging seat having two inclined portions separated by a face which faces generally inward and away from the door opening, the inclined portions facing generally inward and toward the door opening;   a fuselage engaging seat on the door which has two inclined portions separated by a face for mating with the door engaging seat; and   the face on the door engaging seat being oriented at a selected acute angle relative to a line perpendicular to the outer surface of the wall nearest the door engaging seat, the acute angle being selected such that an inward directed force component on the door transmitted through the mating faces due to tension from a pressure differential on the fuselage is less than the outward directed force component on the door due to the pressure differential on the fuselage.   
     
     
       13. The door assembly of claim 12, further comprising: a straight door engaging seat at the straight portions of the door opening, the straight door engaging seat having a door engaging face oriented at a selected acute angle relative to a line perpendicular to the outer surface of the fuselage; and   a straight fuselage engaging seat at mating straight portions of the perimeter of the door, having a fuselage engaging face parallel to and engaging the door engaging face when the door is in the closed position, the acute angle being selected such that an outward directed force component of hoop tension due to the acute angle and an outward directed force component of pressure differential on the door are greater than friction between door engaging faces, wherein the door closes itself under the influence of differential pressure.   
     
     
       14. The door assembly of claim 13, further comprising: a latch for securing the door within the door opening when the pressure differential is insufficient to hold the door in place.